If you just want to turn one rad off just turn of the valve with the proper handle/knob on it at one end
If you want to remove the rad turn of the valves at both ends and remove the rad from the valves leaving the valves attached to the pipes... all the water in the rad will drain out as soon as you remove though.
You will need a screwdriver to turn off the end that is not controlled by a hand-turning valve, and then you will need two pipe wrenches, muscles and a shallow bowl to remove the rad completely.
you'll also maybe need to check how the removal of the rad affects the whole performance of your heating system.
It would depend on how your radiators are connected. (See the diagram in the link below). If they're connected in series, closing off one will close off all of them. But if they're in parallel, you can close off one without affecting any of the others. It's quite normal for some radiators in a property to be connected in series, and some in parallel. Up to you to find out!